Synthetic ripple regulator

• US 20030142519A1
• Filed: 09/06/2002
• Published: 07/31/2003
• Est. Priority Date: 01/29/2002
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Walters, Michael M., Wiktor, Stefan Wlodzimierz, Muratov, Vladimir
• Granted Patent: US 6,791,306 B2
• Time in Patent Office: Days
• US Class Current: 363/89
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A synthetic ripple regulator for a DC-DC converter generates an auxiliary voltage waveform that effectively replicates the waveform ripple current through an output inductor, and uses the auxiliary voltage waveform to control toggling of a hysteretic comparator. In a non-limiting implementation, a transconductance amplifier monitors the voltage across the inductor, and supplies an inductor voltage-representative current to a ripple waveform capacitor, so as to produce the auxiliary voltage waveform. Using the replicated inductor current for ripple regulation results in low output ripple, input voltage feed forward, and simplified compensation.

Claims

1. For use with a DC-DC voltage converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing first and second electronic devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor to a regulated voltage output voltage terminal and a capacitor, a method of controlling the generation of said PWM switching signal comprising the steps of:

(a) generating a ripple waveform, and combining said ripple waveform with the voltage at said regulated voltage output voltage terminal to produce a resultant ripple waveform; and

(b) controlling the generation of said PWM switching signal in accordance with said resultant ripple waveform.

2. The method according to claim 1, wherein step (b) comprises coupling said resultant ripple waveform to a hysteretic comparator which controls the generation of said PWM switching signal.

3. The method according to claim 1, wherein step (a) comprises generating said ripple waveform by monitoring the voltage across said inductor.

4. The method according to claim 3, wherein step (a) comprises coupling the voltage across said inductor to a circuit containing a transconductance amplifier circuit, the output of which provides an inductor voltage-representative current proportional to the voltage across said inductor, and supplying said inductor voltage-representative current to a capacitor, to produce said resultant ripple waveform.

5. The method according to claim 4, wherein step (b) comprises coupling said resultant ripple waveform to a first input of a hysteretic comparator, which controls the generation of said PWM switching signal.

6. The method according to claim 5, wherein step (b) further includes comparing the output voltage at said output voltage terminal with a prescribed DC reference voltage to produce an error voltage, and coupling said error voltage to a second input of said hysteretic comparator.

7. The method according to claim 3, wherein step (a) comprises coupling voltage nodes at respective ends of said inductor to first and second transconductance amplifier circuits, outputs of which are controllably switched to provide an inductor voltage-representative current proportional to the voltage across said inductor, and supplying said inductor voltage-representative current to a capacitor, to produce said resultant ripple waveform.

8. The method according to claim 1, wherein step (a) comprises generating said ripple waveform as an auxiliary voltage waveform that effectively replicates a ripple current through said inductor.

9. In a DC-DC voltage converter having a controller, which generates a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing electronic devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor to a regulated voltage output voltage terminal and a capacitor, the improvement comprising:

a ripple waveform generator which is operative to produce a ripple waveform, and to combine said ripple waveform with the voltage at said regulated voltage output voltage terminal to produce a resultant ripple waveform; and

a coupling circuit that is operative to couple said resultant ripple waveform to said controller in such a manner that said controller controls the generation of said PWM switching signal in accordance with said resultant ripple waveform.

10. The improvement according to claim 9, wherein said controller includes a hysteretic comparator which controls the generation of said PWM switching signal, and wherein said coupling circuit is configured to couple said resultant ripple waveform to said hysteretic comparator.

11. The improvement according to claim 9, wherein said ripple waveform generator is operative to generate said ripple waveform in accordance with the voltage across said inductor.

12. The improvement according to claim 11, wherein said ripple waveform generator includes a transconductance amplifier circuit coupled to monitor the voltage across said inductor, said transconductance amplifier circuit supplying an inductor voltage-representative current proportional to the voltage across said inductor to a capacitor, so as to produce said resultant ripple waveform.

13. The improvement according to claim 11, wherein said ripple waveform generator includes first and second transconductance amplifier circuits, having outputs coupled through a controllable switch to provide an inductor voltage-representative current proportional to the voltage across said inductor, said controllable switch supplying said inductor voltage-representative current to a capacitor, to produce said resultant ripple waveform.

14. The improvement according to claim 12, wherein said controller includes a hysteretic comparator which controls the generation of said PWM switching signal, and wherein said coupling circuit is configured to couple said resultant ripple waveform to said hysteretic comparator.

15. The improvement according to claim 14, wherein said coupling circuit is operative to couple said resultant ripple waveform to a first input of said hysteretic comparator, and further including an error amplifier, which is operative to compare the output voltage at said output voltage terminal with a prescribed DC reference voltage to produce an error voltage, and wherein said error voltage is coupled to a second input of said hysteretic comparator.

16. A synthetic ripple regulator comprising:

a controller, which is operative to generate a pulse width modulation (PWM) switching signal that switchably controls operation of a switching circuit containing electronic devices coupled between respective power supply terminals, and having a common node thereof coupled through an inductor to a regulated voltage output voltage terminal and an output capacitor;

a ripple waveform generator which is operative to generate a ripple waveform and to combine said ripple waveform with the voltage at said regulated voltage output voltage terminal to produce a resultant ripple waveform; and

a hysteretic comparator, which is operative to control generation of said PWM switching signal in accordance with said resultant ripple waveform.

17. The synthetic ripple regulator according to claim 16, wherein said ripple waveform generator is operative to generate said ripple waveform by monitoring the voltage across said inductor.

18. The synthetic ripple regulator according to claim 17, wherein said ripple waveform generator includes a transconductance amplifier circuit coupled to monitor the voltage across said inductor, said transconductance amplifier circuit supplying an inductor voltage-representative current proportional to the voltage across said inductor to a ripple waveform capacitor, so as to produce said resultant ripple waveform.

19. The synthetic ripple regulator according to claim 17, wherein said ripple waveform is coupled to a first input of said hysteretic comparator, and further including an error amplifier, which is operative to compare the output voltage at said output voltage terminal with a prescribed DC reference voltage to produce an error voltage, and wherein said error voltage is coupled to a second input of said hysteretic comparator.

20. The synthetic ripple regulator according to claim 17, wherein said ripple waveform generator includes first and second transconductance amplifier circuits, having outputs coupled through a controllable switch to provide an inductor voltage-representative current proportional to the voltage across said inductor, said controllable switch supplying said inductor voltage-representative current to a ripple waveform capacitor, to produce said resultant ripple waveform.